Yeah, yeah, that's what they say. The customer is always right. I've said it before. And it's a good rule. Most of the time. Almost all of the time. But there are exceptions. You will know when they are. It will be those times when you will feel like scum of the earth and will not be able to respect yourself, ever, if you roll over and take too much abuse from a customer. Even then, you are not excused to punch their lights out. Not even tell them where to stick it. You will just bite your tounge and politely, or at least evenly disengage yourself from the situation. If the customer isalready emotional, as he most likely is if he's being abusive enough to warrant extreme measures, your further failure to put up with him/her is probably going to escalate her/his abuse. Still you disengage. You try not to make things worse. But you also are not required to stand for being abused. However . . . .
It would be better to take the abuse rather than create a scene, escalate a dangerous situation, or get killed. I'm serious. There may be times when people get crazy on you. If you can deal with it and disengage easily, then do so. Times are tough. LIFE is tough. Emotions are fragile, alchohol and drugs are rampant. Anger is the worst drug of all. You do not want to become the recipient of a drugged-up crazo's unleashed anger just to sooth your ego. So, what am I saying? Do you or don't you? What?
The point is that it is a very tough call. You will know when the line has been crossed. But only after you have considered that you may lose a sale. Or lose money. Or lose your job over your behavior. Or even lose your LIFE. Really. Here's how it is.
I also write a self-defense blog. I teach self defense. I teach knife-lore. I teach remedial shooting for problem shooters who have bad shooting habits or unique eye-coordination. I teach my state's requisite course for applying for a handgun carry permit. I do my best to teach teach how to stay alive and unhurt. The most important rule regarding self-defense is to be nice. Be considerate. Do not antagonize. No mater how bad you think you are. Do unto other as you'd have them do unto you. The insolent young man you dis this morning may execute your tonight. Really! It happens.
So, the rule is, there is no hard and fast rule. But after you have considered all the options and all the possible consequenses, at the end of the day, only you will know what to do. Schooled intuition is worth a lot. A knee-jerk reaction is mindless.
In my entire career, having dealt with thousands of transactions of all kinds with all kinds of people--not a small number that were with what I call horse-traders of every disposition and variety--I have felt that the line was crossed, maybe five times. I still feel that my judgement was correct in every case. However, I will also tell you that I nearly lost my life in one of those cases. Be your own judge. Just remember someone else may choose to be your judge, jury, and executioner.
The customer is not always right. but not very often.